This invention relates generally to high power semiconductor laser diodes and, more particularly, to semiconductor laser diode drive circuits or drivers. Semiconductor laser diodes are widely used in a variety of applications. The present invention pertains specifically to semiconductor laser diodes of the type used in optical communication in space and in research laboratory applications. Devices of this general type are typically driven at high modulation currents, of approximately 200 mA peak-to-peak, and high data rates, such as 600 Mbit/s (megabits per second). In a communications application, the semiconductor laser diode is biased by a relatively low bias current to produce a low intensity output and is modulated by a data signal that switches the diode back an forth between the low intensity output condition and a high intensity output condition.
Associated with the laser diode is a drive circuit that supplies both a bias current and a modulation current controlled by the data signal. Traditional designs have integrated the laser diode with its driver components. Typically, the laser diode plugs into a socket that is part of a driver assembly. The principal drawback with this approach is that thermal power dissipated by the driver heats up the laser diode, which becomes degraded in spectral purity. Thus the useful life of the laser diode is severely limited.
Although thermo-electric coolers (TECs) have been used to maintain laser diodes at a desired operating temperature, their use is rendered extremely difficult by the close proximity of the heat dissipating laser diode driver. Ideally, designers would like to isolate the laser diode both physically and thermally from its driver, but no-one prior to the present invention has achieved this goal.